托福阅读背景知识：兴奋剂有害健康.docxVIP

智课网TOEFL备考资料 托福阅读背景知识：兴奋剂有害健康 摘要： 托福阅读背景知识：兴奋剂有害健康。小马小编为各位考生整理托福背景知识，下面就请大家跟随小编一起来了解这些背景知识吧。  每四年一届的奥运会赛场上，经常被爆出某某国家的运动员涉嫌使用兴奋剂等消息，所以我们对兴奋剂并不陌生。运动员们之所以使用兴奋剂是由于在使用后，身体素质处于极度兴奋的状态，这样就可以提高自己的成绩。但是科学研究证明，使用兴奋剂会对人的身心健康产生许多直接的危害，使用不同种类和不同剂量的禁用药物，对人体的损害程度也不相同。还有一点也是对运动员不公平，所以目前兴奋剂是严于使用的。今天 托福 培训频道的小编及为大家来讲解下与兴奋剂相关的一些知识来扩充我们的知识面。  From federal investigations into Major League Baseball(美国职业棒球大联盟) to allegations of substance abuse in track and field, performance enhancing drugs(兴奋剂) have been in the news a lot. The most well-known performance enhancers are steroids(类固醇), drugs that can make athletes bigger and stronger. But they can also cause serious medical problems.  So how do steroids work, and what makes them so dangerous?  First, it’s important to understand that the body naturally produces steroids. For men, the best known is testosterone(睾丸激素). Testosterone is an anabolic steroid(合成代谢类固醇), meaning that it encourages new muscle growth. So the more testosterone you have in you, the greater potential you have to be bigger and stronger. It makes sense, then, that artificial anabolic steroids mimic testosterone produced in the body.  Here’s how they work. Anabolic steroids attach to cells and encourage them to produce more protein, which muscles need to grow and become stronger. So steroids basically (1)speed up and enhance the process of muscle growth that you can accomplish by lifting weights and other kinds of exercise. A weightlifter on steroids will develop larger muscles and do so faster than a “clean” weightlifter.  Millions of people take performance enhancing drugs such as caffeine and vitamins every day. But unlike these drugs, steroids can cause serious, long lasting problems. For example, steroid use puts extra pressure on the liver to cleanse the bloodstream of the many toxins in steroids.  Prolonged steroid use can result in liver damage. They also affect brain chemistry(脑化学), and can cause depressi